Capture suddenly (4)
(Other definitions for snag that I've seen before include "Catch -- problem" , "Minor difficulty" , "Hitch, unexpected problem" , "Unforeseen obstacle" , "Disadvantage - small hole in fabric" .)
(Other definitions for snare that I've seen before include "Gin, possibly" , "part of a musician's kit" , "Catch" , "Lure or trap" , "Noosed trap" .)